The aeronautical industry has gradually increased its demand for greater cooling power for on-board electro-electronic equipment. This increased cooling power demand is evident with the advent of transport category aircraft that depend more heavily on electrically powered on-board systems that have been implemented to replace the more conventional pneumatic and/or hydraulic power-based systems, such as electric flight control actuators, cabin compressors for environmental control systems and electric heaters for ice protection. As a consequence, the electrical power requirements to assist such electric-powered systems and electronics (motor controllers, power converters and the like) have in turn risen proportionally thereby requiring a greater ability to dissipate more heat. Additionally, as both size and weight are significant penalties for aircraft components, the power density per unit of surface area tends to increase as well. Therefore, in order make it feasible to install on-board electronics with high heat dissipation, it is necessary to implement more efficient techniques to remove heat from such devices.
Aircraft cooling systems currently in use traditionally use air as the working fluid. Natural convection has inherently high thermal resistance between heat sources and sinks. Air forced convection by fans reduces the inefficiency of cooling systems by increasing heat transfer coefficients but the fans generate acoustic noise, consume electrical power, add weight and require periodic maintenance.
Heat transfer devices such as passive thermosyphons and heat pipes can be classified as heat superconductors. Under project constraints, these devices present low thermal resistance and acoustic noise. In addition, power consumption is not required and maintenance is expected to decrease drastically as compared to air-forced convection cooling systems. Therefore, passive thermosyphon heat transfer devices are suitable to be used in aircraft applications.
In the aircraft industry, the application of heat pipes and thermosyphons is limited to compartments where the installation of traditional cooling elements such as ducts and fans is difficult to be accomplished. Cooling techniques based upon heat pipe technology have recently been observed. For example, U.S. Pat. No. 7,505,267 (the entire content of which is expressly incorporated hereinto by reference) discloses the use of heat pipes in a refrigeration circuit for cabin entertainment devices located in areas of difficult heat removal (e.g. within and beneath passengers' seats).
U.S. Pat. No. 7,967,249 (the entire content of which is expressly incorporated hereinto by reference) proposes a refrigeration system with heat pipes, loop heat pipes, a cold storage unit and a fuselage heat exchanger. The system that is proposed by such patent, however, has as several disadvantages including the use of air as the heat transfer media between the equipment and the cooling system, the use of a fan in the electronic equipment compartment and a cold storage unit (which necessarily adds undesirable weight to the system).
What has been needed therefore are lightweight high capacity cooling systems that are especially adapted for on-board use in aircraft. It is towards fulfilling such a need that the embodiments herein are directed.